Flash roasting



Feb. l1, 1936.

INVENTOR Horace Freemaw 31m/w( A'rroRNEYs Feb. 11, 1936. H, FREEMAN A2,030,628

FLASH ROASTING Filed Jan. s,I 1935 2 sheets-Sheet 2 INVENTOR` HoraceFreeman 792,1( MV1/Uf@ AfrroRNEYs the furnace of Fig. 1;

Patented Feb. 11, 1936 n UNITED STATES FLASH ROASTING Horace Freeman,Montreal, Quebec, Canada, assignor to Nichols Engineering & ResearchCorporation of Canada, Limited, Montreal, Quebec, Canada, a corporationof Canada Application January 8, 1935, Serial No. 817

6 Claims.

'I'his invention relates to roasting furnaces and more particularly tofurnaces for flash roasting relatively finely divided ore while insuspension within the roasting chamber of the furnace. Features of thisinvention have been found to be particularly adaptable to the roastingof sulphide ores such as pyrite and pyrrhotite for the production ofsulphur dioxide gas and iron oxide products. However, the invention isadaptable to the roasting of various other `types of ores.

This invention is directed to improvements upon and modifications of theroasting apparatus and methods referred to in my United States PatentNo. 1,812,397 and in my copending applications Ser. No. 433,471, filedMarch 5, 1930, Ser. N0. 601,138, filed March 25, 1932 and Ser. No.633,439, led September 161932, reference to which is hereby made for amore complete description of such portions of the furnace and auxiliaryapparatus and methods as may 'not be fully explained or repeatedhereinafter.

The invention is especially directed to features of construction andmethods for introducing the finely divided ore into the flash roastingchambers of furnaces of the types described in the above mentionedpatent and applications, in such manner that the ore will be properlydistributed and maintained in suspension to enable the methods referredto in 4said patent and applications to be carried out with a high degreeof eiiiciency` and economy.

The invention consists of such novel featurea' arrangements,combinations of parts and methods. as maybe shown and described inconnection oi?v a furnace construction embodying the invention;

Fig. 2 is a vertical sectional view of a nozzle assembly for introducingthe ore into the top of Fig. 3 is a top or plan view of the assembly ofFig. 2;

Fig. 4 is a detailed view partly in section o1' the inner member orturbine of the assembly of Fig. 2; and

(Cl. 26S-20) Fig. 5 illustrates in perspective the said turbine member.

The furnace as shown in Fig. 1 may comprisel a relatively tall andsubstantially cylindrical roasting chamber having side walls as at I0 ofa suitable refractory material, a somewhat arched roof I I of similarmaterial and a converging relatively cone shaped lower portion I2terminating at the bottom with a cinder outlet as at I3.

The relatively finely divided ore to be roasted may be introduced with astream of air or other oxidizing fluid, through thenozzle assembly as atI4, preferably located substantially at the middle of the top or roof ofthe furnace. With the .nozzle assembly constructed in the mannerhereinafter described, the ore particles are carried into the roastingchamber at a relatively low velocity and are distributed in the-chamberwith considerable turbulence while being met by an additional supply ofuprising air or other oxidizing fluid introduced through the cinderoutlet I3, The gaseous products of combustion are preferably Withdrawn`from the furnace through one, two or more gas outlets as at I5, locatedin the Walls of theupper portion' of the chamber. The gaseous productsof combustion are preferably withdrawn by a suitable suction fan capableof drawing into the roasting chamber through the cinder outlet I3, asufficient supply of uprising air to maintain the falling particles insuspension for a short period and to provide an oxidizing mediumsuiilcient when taken with that introduced through the nozzle, to causethe ore to be roasted to the desired degree.

The construction and operation of the nozzle assembly I4 and itsassociated parts will now be described. As above stated, thisassembly ispreferably located either at or adjacent the middle of the roof ofthefurnace in order that the falling shower of ore particles will bemaintained in a more or less concentric relationship to the walls of thefurnace, thus substantially avoiding con' tact of the falling particleswith the furnace walls, since under some circumstances contact of theparticles while being roasted, with the walls, may result in troublesomeaccumulations on the walls. The nozzle assembly may preferably bemounted in a cylindrical nozzle protecting member as at I6, supported bysuitable framework as at I1 and extending down through the roof II ofthe furf nace and terminating substantially` flush with the innersurface of the roof. A cylindrical nozzle member I8 may be removablymounted within this protective member. If desired', the members I6 andI8 may be of such diameters as shown `from the outer surface of theportion 23.

and oxidizing medium to the furnace. The bottom edgesV or the outlet.portions of the member I8 may preferably be somewhat constricted as at2| for aiding in the control of the falling stream of ore and oxidizingmedium.

A turbine member 22 may be removably mounted .within and adjacentthe'lower end of the nozzle member I 8. This turbine member which isillustrated in detail in Figs. 3,-5, may comprise a central portion asat 23, preferably substantially cylindrical, forming a central ver`tical opening for directing a part of the ore -stream downwardlysubstantially axially of the furnace. This portion may be surrounded bya plurality of outer openings formed by a plurality of blades or vanesas at 24, which may be conveniently cast integrally with the portion 23and extend in a. generally radial direction outwardly 'This turbinemember my be heldin place. within the.nozzle member I8 as by one or morelugs or threaded pins as at 25 extending through -the walls of themember I8 and engaging lugs as at 26 formed on the vanes 24. The variousblades or vanes 24 are preferably made alike and the active surfacesthereof start at the top in a substantially vertical'position, thesesurfaces being gradually curved so that at the bottom edges of theblades, the surface extends to a substantially acute angle in respect toa vertical plane. Although `the curvature of these blades may be variedsomewhat, depending upon the proportions 'of the furnace, the kind oforetreatedv andthe pressure of the ore and oxidizing medium as in.-troduced through the nozzle. in the preferred example illustrated, thehorizontal elements of the active surfaces of these blades may comprisesubstantially straight and radial lines, so arranged that the surfacesprogress from a vertical position at the top edge of theblades graduallyto an acute angle to the vertical at the bottom edges of theblades. Asindicated in Fig. 2, the outer ends of the blades do not need to extendto the walls of the nozzle throughout their height. 4.In operationtheoxidizing medium and finely divided ore, preferably of a substantiallyuniform mixture, may be blown through a suitable conduit connected tothe top of the nozzle whereby the mixturepasses downwardly through thenozzle under a relatively low pressure, for example, positive staticprssure of from l" to 4':

Y w. g. Under normal operating conditions with a furnace and with anozzle of the proportions indicated in the drawings forthe roasting ofpyr'ite, I have found that pressures of from '1/2" to 1" w. g. give mostsatisfactory results. However, if a portion of the outlet gases arerecirculated back into the nozzle intake for the purpose of improvingtemperature control conditions within thefurnace, it may be desirable toincrease the pressures somewhatascompared with those last above stated.The pressure should preferably be too highl lest the'ore particles bedriven into the combustion chamber too rapidiy to permit time.

for complete combustion. Also,' if the pressure is too high, oreparticles may impinge upon the f furnace walls, which may lead to thedifficulty above mentioned, i. e., the formation of troublesomeaccumulations on the walls. 'I'he pressure should also be suillcientlylow so that gas is not driven'out through the cinder opening at thebottom of the furnace. 1

In passing through the nozzle member I 8, a substantial part of theincoming ore and oxidizing medium pass down through the central openingin the cylindrical portion 23. This stream of the material acts as anaxis, giving direction to the ore and gases'. The remainder of the oreand oxidizing medium pass through the outerv openings between the blades24, much of it impinging against the curved surfaces of the blades, so'that these outer streams are given a rotational movement providing `jetswhich intersect and cut into and through the central `jet. 'This resultsin a substantial turbulence of the ore and oxidizing medium. scatteringthe same as ar downwardly expanding cone, which however does not extendto its maximum dimensions until at its portions of maximum diameter, dsnot extend into substantial contact with the furnace walls.

With the nozzle parts of the relative proportions substantially as shownin the drawings `and with the nozzle member I8 having an inside diameterof approximately l ft., I have found that a. furnace chamber having aninside diameter of about 11 ft. and with vertical dimensions in -theproportion shown in Fig. 1, gives excellent results. However, with sucha nozzle, the furnace diameter may well be varied from, in theneighborhood of 10 ft. to vliift. depending upon the character of theorebeing treated, and various other conditions. l

The height of the turbine member 22 within the nozzle member I8 may besuitably adjusted by' trialuntil the best roasting conditions ,are

secured, and this member may then be ilxed in the desired positionbyproperly 'locatingthe threaded pins 25 in the nozzle walls. Intheevent it is desired to alter the roasting conditions or treat variousdifferent ores, the turbine medium from the cinderoutlet Il, with thegasesr of combustion going out the outlets at the top, is more fully setforth in the above mentioned copending applications. 1

I find that the outlet of the nozzleas'sembly should preferably justproject through the 'roof of the furnace, whereas if it projects downinto 'the furnace` to any y. great extent, interfering crusts mayaccumulate on its'outside walls, `ultimately obstructing the flow at theoutlet of the nozzle and interfering with its proper vdetail withrespect to' a preferred and satisfactory example, it will be understoodby those skilled in the art after understanding the invention as abovedescribed,` that various changes and modiiications may be made withoutdeparting from the,spirit and scope of the invention, and it is intendedtherefore in thedappended claims to cover all such changes andmodications. f

What is claimed as new and is desired to be secured by Letters Patentis:

1.l In a furnace for ash roasting finely divided ore particles insuspension, a roasting chamber, a nozzle at the midportion of the roofof said chamber for introducing the ore particles with a stream ofgaseous medium, an opening being pro'- vided within said nozzle fordischarging the central portion of said stream in a vertically downwarddirection, said opening being surrounded by an annular space providingadditional 'ore discharge openings within said nozzle, and a pluralityof curved vanes within said annular space for creating a turbulentcondition in the ore and gaseous medium passing through said annularspace.

2. In a furnace for ash roasting ilnely divided ore particles insuspension, a roasting chamber, a nozzle at the upper part of saidchamber for introducing the ore particles with a stream of gaseousmedium, ,means xed within said nozzle adjacent its outlet forcontrolling a spray of the o re particles from 4the nozzle, said meanshaving a central portion with an opening for discharging a central jetof the particles substantially axially of .the spray, and a plurality ofvanes extending fromsaid central portion for engaging ore particlesforming the part of the spray surrounding Asaid central jet, said vaneshaving curved surfaces for creating a turbulent condition in saidsurrounding portions of the stream, and said turbulent conditionextending into said central jet whereby the ore is distributed as adownwardly expanding conical spray.

3. In a'furnace for flash roasting finely di-V vided ore particles insuspension, a roasting chamber, a nozzle at the midportion of the roofof said chamber for introducing the ore particles with a stream ofgaseous medium, means within said nozzle and adjacent its outlet forcontrolling the form lof the spray of ore emanating therefrom, saidmeans having a central opening for discharging the middle portion ofsaid spray in a vertically downward direction, and a plurality of vanessurrounding said central opening for engaging the ore forming outerparts of said spray and for imparting to said outer parts a turbulentfined within a downwardly expanding conical space.

5. In a furnace for flash roasting iinely divided ore particles insuspension, a roasting chamber,

a nozzle at the `midportion of the` roof ofsaid 'chamber for introducingthe ore particles with a stream of gaseous medium, an opening beingprovided within said nozzle for discharging the central portion `oi saidstream in a vertically downward direction, said opening being surroundedby an annular space providing additional ore discharge openings withinsaid nozzle, a plurality of curved vanes within said annular space forcreating a turbulent condition in the ore and gaseous medium passingthrough said annular space, means for introducing at the f.-

lower part of said chamber an uprising supply of gaseous medium,andoutlet means at the upper part of the chamber for the gases ofcombustion.

6. A process of roasting ores which comprises introducing the same infinely dividedL form into the top of a roasting chamber with a stream ofair or other oxidizing medium under a relatively low pressure,controlling said ore particles as a falling spray consisting of avertically downwardly directed central jet surrounded by a turbulentannular rotating downwardly expanding jet intersecting said central jetand distributing the ore as a falling spray substantially confinedwithin a downwardly expanding conical space, introducing an uprisingstream of gaseous medium in the chamber, and. withdrawing the 'gaseousproducts of combustion from the upper portion of the chamber.

HORACE FREEMAN.

